Long-Term Follow-Up in Patients Undergoing Renal Mass Biopsy: Seeding is not Anecdotal.

INTRODUCTION: Renal biopsy is recommended if the outcome might alter therapeutic decisions for patients who present with renal masses of unclear etiology. However, little is known about long-term risks related to this procedure. PATIENTS AND METHODS: We performed a retrospective analysis of an institutional database maintained by a tertiary referral center that included patients who underwent renal biopsies between 2003 and 2005 with a follow-up of at least 15 years. Renal biopsies were taken percutaneously with a coaxial technique according to guideline recommendations and included off-line ultrasound guidance. RESULTS: We identified 106 patients who underwent biopsies for a renal mass of unclear etiology. The median age was 58.7 years (43.7-66.2). A median of 4.2 (3-6) biopsies were collected from each patient. Tumor seeding leading to local growth was identified in 6 patients (5,7%) after a median follow-up of 8.2 years. Four of these lesions that were resected exhibited the same histology as the original biopsy result; these patients experienced no further recurrence. In 45 patients (42%), the biopsy results led to a therapy other than surgery (n = 28 lymphoma, n = 6 metastasis from other malignancies, n = 11 oncocytoma). The remaining 61 patients (58%) were diagnosed with renal cell carcinoma treated either surgically or with ablation. None of the patients developed metastatic spread related to tumor seeding. CONCLUSION: Tumor seeding after renal mass biopsy is a rare, but relevant risk associated with this procedure. As indications for renal mass biopsy increase, longer-term follow-up and improved biopsy techniques should be considered to address this complication.